scholarly journals Sea otter dental enamel is highly resistant to chipping due to its microstructure

2014 ◽  
Vol 10 (10) ◽  
pp. 20140484 ◽  
Author(s):  
Charles Ziscovici ◽  
Peter W. Lucas ◽  
Paul J. Constantino ◽  
Timothy G. Bromage ◽  
Adam van Casteren
Keyword(s):  
Dental Enamel ◽  
Modern Human ◽  
Sea Otter ◽  
Human Teeth ◽  
Human Enamel ◽  
Chip Size ◽  
Fossil Hominins ◽  
On Chip ◽  
Fossil Hominin ◽  
Enamel Prism

Dental enamel is prone to damage by chipping with large hard objects at forces that depend on chip size and enamel toughness. Experiments on modern human teeth have suggested that some ante-mortem chips on fossil hominin enamel were produced by bite forces near physiological maxima. Here, we show that equivalent chips in sea otter enamel require even higher forces than human enamel. Increased fracture resistance correlates with more intense enamel prism decussation, often seen also in some fossil hominins. It is possible therefore that enamel chips in such hominins may have formed at even greater forces than currently envisaged.

scholarly journals Assessing the predictability of existing water-to-enamel geolocation models against known human teeth

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Momoko Ueda ◽  
Lynne S. Bell
Keyword(s):  
Drinking Water ◽  
Stable Isotope ◽  
Stable Isotope Analysis ◽  
Isotope Analysis ◽  
Dental Enamel ◽  
Threshold Value ◽  
Human Teeth ◽  
Country Level ◽  
Water Oxygen ◽  
Human Enamel

AbstractStable isotope analysis of human tissues has become a valuable tool for mapping human geolocation. This study adds to the existing knowledge of the relationship between oxygen stable isotopes in human enamel and drinking water by presenting enamel oxygen values in clinic-extracted human dental enamel with known provenance. The results from this study indicate that the theoretical isotopic relationship between enamel and drinking water oxygen is weak at the city and country-level. Differences of up to 15‰ were observed between predicted drinking water oxygen values using existing models and observed values, highlighting the complexity of using water/enamel conversion equations. The lower isotopic boundary of enamel oxygen values is now understood for Metro Vancouver at δ18Oc(VPDB) = – 11.0‰ and presents the possibility of using stable isotope analysis as an exclusionary tool where individuals falling below threshold value can be identified as non-local. Overall, this study’s results support the development of geographical reference maps for human enamel oxygen.

scholarly journals Assessing the Predictability of Existing Water-to-enamel Geolocation Models Against Known Human Teeth: Do We Need Tissue-Specific δ 18O Reference Maps?

2021 ◽  
Author(s):  
Momoko Ueda ◽  
Lynne S. Bell
Keyword(s):  
Isotope Analysis ◽  
Dental Enamel ◽  
Human Teeth ◽  
Tissue Specific ◽  
Country Level ◽  
Human Enamel ◽  
Metro Vancouver ◽  
Oxygen Stable Isotopes ◽  
Stable Oxygen ◽  
The City

Abstract Stable isotope analysis of human tissues has become a valuable tool for mapping human geolocation. This study adds to the existing knowledge of the relationship between oxygen stable isotopes in human enamel (δ 18Oenam) and drinking water (δ 18Odw) by presenting δ 18Oenam values in clinic-extracted human dental enamel with known provenance. The results from this study indicate that the theoretical isotopic relationship between 18Oenam and 18Odw is valid although weak at the city and country-level. However, differences of up to 15‰ were observed between predicted δ 18Odw values using existing models and observed values, highlighting the complexity of using enamel-to-water conversion equations. A city-specific range of δ 18Oenam values is now understood for Metro Vancouver [δ 18Ocarbonate = − 9.7‰ to − 7.2‰] and presents the possibility of both including within the city of Vancouver and excluding individuals, utilizing stable oxygen analysis as an exclusionary tool. Overall, this study’s results support the development of tissue-specific d 18Oenam geographical reference maps for human geolocation.

Human Enamel Replication

1976 ◽  
Vol 34 ◽  
pp. 180-181
Author(s):  
Norman L. Dockum ◽  
John G. Dockum
Keyword(s):  
Organic Matrix ◽  
Human Teeth ◽  
Human Enamel ◽  
Straight Line ◽  
Ultrastructural Characteristics

Ultrastructural characteristics of fractured human enamel and acid-etched enamel were compared using acetate replicas shadowed with platinum and palladium. Shadowed replications of acid-etched surfaces were also obtained by the same method.Enamel from human teeth has a rod structure within which there are crystals of hydroxyapatite contained within a structureless organic matrix composed of keratin. The rods which run at right angles from the dentino-enamel junction are considered to run in a straight line perpendicular to the perimeter of the enamel, however, in many areas these enamel rods overlap, interlacing and intertwining with one another.

Readjustment of the Standard ASUDAS to Encompass Dental Morphological Variations in Plio-Pleistocene Hominins

2018 ◽  
Vol 30 (1-2) ◽  
pp. 32-48
Author(s):  
M. Louail ◽  
S. Prat
Keyword(s):  
Phylogenetic Relationships ◽  
Homo Sapiens ◽  
Initial Study ◽  
Morphological Characters ◽  
State University ◽  
Arizona State University ◽  
Dental Anthropology ◽  
Morphological Variations ◽  
Fossil Hominins ◽  
Fossil Hominin

The standard ASUDAS scoring system (Arizona State University Dental Anthropology System) is used to assess dental morphological variations in modern humans. It is also frequently used to study, score, and compare morphological variations in fossil hominin taxa and to examine their phylogenetic relationships. However, using ASUDAS in studies of this type is under debate because it is based on modern Homo sapiens populations and does not appear to cover all variations observed in fossil Plio-Pleistocene homi- nins. Our observations and coding of 178 dentals casts of Plio-Pleistocene specimens based on ASUDAS and from the literature have confirmed the need to adapt the standard system to fossil hominins. In this initial study, we propose that the scoring procedures for some morphological characters need to be readjusted, while others could be standardized following the ASUDAS system.

Nanoscale Characterisation of Salivary Pellicle

2004 ◽  
Vol 841 ◽  
Author(s):  
Michelle E. Dickinson ◽  
Adrian B. Mann
Keyword(s):  
Dental Enamel ◽  
Tooth Surface ◽  
Surface Adhesion ◽  
Human Enamel ◽  
Oral Physiology ◽  
Salivary Pellicle ◽  
Initial Adsorption ◽  
Dietary Agents

ABSTRACTSalivary pellicle is an organic biofilm formed by the physisorption of proteins and carbohydrates onto the surface of dental enamel exposed to the oral environment. The pellicle has several key roles in oral physiology including lubrication and reduction of friction between teeth during mastication, as well as chemical protection of the enamel against acidic solutions. However, pellicle proteins are known to react with dietary compounds to cause extrinsic staining on the tooth surface.In this study, nanoindentation and AFM have been used in vitro to examine the acquired salivary pellicle formed in vivo on dental enamel. The mechanical properties, growth, structure and morphology of pellicle grown in vivo on human enamel surfaces have been analysed. In addition, the effects of dietary agents such as polyphenols on the pellicle's morphology and properties have been studied.It was found that initial adsorption of proteins on the enamel surface occurred within 30 seconds of exposure to the oral cavity, with full growth achieved within 2 hours. Differences in the properties of the pellicles such as surface adhesion, and time dependent effects due to polyphenol interaction were measured using nanoindentation. It was seen that the polyphenol interaction has a significant effect on these properties. These results suggest that the stained pellicle is mechanically stiffer, but also less viscous and more fluid like. This could explain why traditional tooth brushing techniques do not efficiently remove this layer.

scholarly journals Recent origin of low trabecular bone density in modern humans

2014 ◽  
Vol 112 (2) ◽  
pp. 366-371 ◽  
Author(s):  
Habiba Chirchir ◽  
Tracy L. Kivell ◽  
Christopher B. Ruff ◽  
Jean-Jacques Hublin ◽  
Kristian J. Carlson ◽  
...  
Keyword(s):  
Body Size ◽  
Trabecular Bone ◽  
Homo Sapiens ◽  
Modern Human ◽  
Homo Erectus ◽  
Lower Limbs ◽  
Modern Humans ◽  
Human Skeleton ◽  
Trabecular Density ◽  
Fossil Hominins

Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

Current and Future Three-Dimensional LSI Integration Technology by “chip on chip”, “chip on wafer” and “wafer on wafer”

2006 ◽  
Vol 970 ◽  
Author(s):  
Manabu Bonkohara ◽  
Makoto Motoyoshi ◽  
Kazutoshi Kamibayashi ◽  
Mitsumasa Koyanagi
Keyword(s):  
Three Dimensional ◽  
Process Time ◽  
Future Technology ◽  
Sensor Device ◽  
Research Level ◽  
Key Technologies ◽  
The Future ◽  
Chip Size ◽  
On Chip ◽  
Chip Chip

ABSTRACTRecently the development of three dimensional LSI (3D-LSI) has been accelerated and its stage has changed from the research level or limited production level to the investigation level with a view to mass production. This paper describes the current and the future 3D-LSI technologies which we have considered and imagined. The current technology is taken our Chip Size Package (CSP) for sensor device, for instance. In the future technology, there are the five key technologies are described. And considering con and pro of the current 3D LSI stacked approach, such as CoC (Chip on Chip), CoW (Chip on Wafer) and WoW (Wafer on Wafer), We confirmed that CoW combined with Super-Smart-Stack (SSS™) technology will shorten the process time per chip at the same level as WoW approach and is effective to minimize process cost.

Effect of Aggregate Size on the Retention of Conventional and Rubberized Chip Seal

2019 ◽  
Author(s):  
Alireza Pourhassan ◽  
Ahmed A. Gheni ◽  
Mohamed A. ElGawady
Keyword(s):  
Impact Load ◽  
Mechanical Energy ◽  
Aggregate Size ◽  
Crumb Rubber ◽  
Superior Performance ◽  
Natural Aggregate ◽  
Modes Of Failure ◽  
Chip Seal ◽  
Chip Size ◽  
On Chip

<p>A common defect of chip seals is chip loss or raveling. The previous studies showed uniform grading of aggregate will enhance the retention ability of the chip seal. Also, it was shown that using crumb rubber as an aggregate will enhance the chip seal behavior including aggregate retention. However, no specific study has been done focusing on the effect of aggregate size for rubber nor natural aggregate. This paper is evaluating the effect of chip size on aggregate retention of both natural and rubber aggregate. Standard and modified Vialit tests, and standard and modified Pennsylvania tests which apply different forms of mechanical energy in different temperature was used to assess the aggregate-binder bond interaction and study the chip seal retention. Test results showed different trends for the effect of size on chip retention under impact load versus dynamic load because of different modes of failure. However, rubber particles showed a superior performance rather than natural aggregate in all cases.</p>

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